At present duvets, sleeping bags and the like items which are constructed with elongate compartments are normally filled with a particulate material like down, feathers, wool, and more recently with the soft knops invented by the applicants and the subject of U.S. Pat. No. 4,761,857. The particulate material in the compartments forms a lightweight mass which acts as a padding and insulation material.
A problem with these padding materials is that it is difficult to fill the compartments evenly. This method differs in concept from prior art methods such as in McJoynt, U.S. Pat. No. 2,060,629 in that it is specifically designed for fi ling compartmented products with low density fills without the tendency to compress the fill. The machine has been specifically designed for filling duvets. The concept for a duvet is to have "warmth without weight". Typically, fill weights of less than 500 g per square meter are required, which can only be achieved with lightweight fills which would be capable of filling a space of more than forty millilitres per gram. To achieve these low weights a vacuum created by a pulsed venturi is needed to draw off discreet amounts of fill material from a fluidized reservoir. These discreet amounts are then transported down elongate members to the closed end of the compartments and deposited there by short pulses of air without compressing the fill. It was found in trials that if a continuous supply of air was used, as would be produced by a fan such as in the above-noted prior art patent to Mcjoynt, the fill would be unduly compressed into the compartments, or, alternatively, if the air pressure was reduced to overcome compressing of the fill material, this could cause obstructions blocking the elongate members. The method is ideally suited to use with soft knops (U.S. Pat. No. 4,761,857) which have a filling capacity of more than 60 ml/g.
Prior art such as McJoynt, Knopp (U.S. Pat. No. 2,721,767) and Jacobsen (U.S. Pat. No. 2,550,354), which are designed to fill densely packed products such as automotive cushions and the like, would compress the particulate materials at the closed ends of the compartments. At present this happens, and the compartments are then smoothed out by hand. This is particularly difficult for soft knops which are not always free flowing, as they have a tendency to form clumps when they are forced along elongate compartments.
An object of the present invention is therefore to provide a method and apparatus for filling compartments in duvets and the like with particulate padding materials.
Further objects of the invention will become apparent from the following description which is given by way of example.